The spun bobbins produced by a spinning machine are supplied to an automatic winding machine in a subsequent step in which a yarn is wound onto a package of a predetermined shape that can hold a predetermined amount of yarn thereon, while removing defects from the yarn.
In the concerned automatic winding machine, the yarn unwound from the spun bobbin passes through a balloon controller and a tension apparatus and is checked by a slab catcher for defects while being wound around a package rotating on a traverse drum. During winding, the yarn is cut when the slab catcher detects the yarn defect and, after removal of the defective portion of the yarn, the yarn on the package side and the yarn on the spun bobbin side are spliced together.
The tension approaches is controlled so that during the unwinding of the spun bobbin, the tension of the yarn winding is controlled so as to become slightly higher than a reference value as winding begins, then to decrease down to the reference value, and to decrease at a predetermined rate relative to the reference value from the start of a decrease in the amount of remaining yarn until winding is complete.
When the slab catcher detects the yarn defect near the winding end of the spun bobbin and winding is restarted after a yarn splicing operation, the yarn winding tension is returned to the value used at the start of winding and is gradually reduced relative to the reference value. In such a case, however, the value does not decrease down to the yarn winding tension used at the winding end, such that the winding tension is increased at the winding end to disturb the shapes of the packages.
It is thus an object of the present invention to solve this problem and to provide a method for operating an automatic winding machine wherein, even if the yarn splicing is executed while the yarn winding tension is decreasing toward the winding end, the subsequent winding tension can be maintained at an appropriate value depending on the amount of the remaining yarn.